Complemented roll attitude flight control system

Abstract

A system and technique is disclosed which provides a complemented roll attitude signal for use in the control system of an aircraft. The complemented roll attitude is produced by combining a yaw rate and true airspeed signal with a conventional roll attitude signal to produce a complemented signal which may be combined with a roll command signal to produce a roll steering signal for controlling aircraft response under non-zero roll attitude conditions of aircraft flight. The complemented roll attitude signal provides improved response to aircraft roll commands under non-zero roll attitude conditions, particularly in helicopter systems.

What is claimed is: 
     
       1. A system for producing an aircraft roll steering signal comprising: means for providing a signal representing aircraft roll attitude;   means for providing a signal representing a combination of aircraft yaw rate and aircraft airspeed;   means for modifying said roll attitude signal with said combined yaw rate and airspeed signal to produce a modified roll attitude signal;   means for combining said modified roll attitude signal with an aircraft roll command signal to produce a signal output; and   means for combining said roll attitude signal with said signal output to produce a roll steering signal.   
     
     
       2. The system of claim 1 wherein said means for providing a signal representing a combination of yaw rate and airspeed comprises: means for providing a signal representing aircraft yaw rate;   means for providing a signal representing aircraft true airspeed;   means for multiplying said yaw rate signal and true airspeed signal and providing a multiplied output signal; and   means for subtracting said multiplied output signal from said roll attitude signal to provide said modified roll attitude signal.   
     
     
       3. The system of claim 1 wherein said means for combining said roll attitude signal with said signal output comprises a summing circuit coupled to subtract said roll attitude signal from said signal output to produce said roll steering signal. 
     
     
       4. The system of claim 1 further comprising means for low pass filtering said modified roll attitude signal to produce a filtered modified roll attitude signal. 
     
     
       5. The system of claim 4 wherein said means for combining said roll command signal and said modified roll attitude signal comprises a means for summing said roll command with said filtered roll attitude signal. 
     
     
       6. The system of claim 4 wherein said means for low pass filtering comprises: a summing circuit having a positive input, a negative input and an output, said positive input being coupled to receive said modified roll attitude signal;   an integrator coupled to the output of said summing circuit for providing an integrated output; and   means for coupling said integrated output to said negative input of said summing circuit for subtraction from said modified roll attitude signal, said integrated output forming said filtered modified roll attitude signal.   
     
     
       7. The system of claim 1 wherein said means for providing a signal representing a combination of yaw rate and airspeed comprises a means for providing a signal representing a combination of yaw rate and true airspeed. 
     
     
       8. A system for providing an aircraft roll steering signal, comprising: means for providing a signal representing aircraft roll attitude;   means for providing a signal representing aircraft yaw rate;   means for providing a signal representing aircraft true airspeed;   means for multiplying said yaw rate signal and said true airspeed signal and providing a multiplied output signal;   means for subtracting said multiplied output signal from said roll attitude signal to provide a modified roll attitude signal;   a summing circuit having a first input, a second input, and an output, said first input being coupled to receive said modified roll attitude signal;   an integrator coupled to the output of said summing circuit for providing an integrated output;   means for coupling said integrated output to said second input of said summing circuit for subtracting said integrated output from said modified roll attitude signal and providing the difference as said summing circuit output;   means for providing an aircraft roll command signal;   means for summing said integrated output with said roll command signal to produce a signal output; and   means for subtracting said roll attitude signal from said signal output to produce a roll steering output signal.   
     
     
       9. A helicopter control system for providing a modified roll steering signal under non-zero roll attitude flight conditions, comprising: means for providing a signal representing a non-zero helicopter roll attitude;   means for providing a signal representing helicopter yaw rate;   means for providing a signal representing helicopter true airspeed;   means for multiplying said yaw rate signal and said true airspeed signal to provide a multiplied output;   means for combining said multiplied output with said non-zero roll attitude signal to produce a modified roll attitude signal;   means for low pass filtering said modified roll attitude signal;   means for combining said filtered roll attitude signal with a roll command signal to produce a signal output; and   means for combining said signal output with said roll attitude signal to produce a roll steering signal having a non-zero value in response to roll commands and a zero value when said roll command signal is zero and said roll attitude signal is non-zero.   
     
     
       10. An aircraft control system for providing a roll steering signal during non-zero roll attitude flight conditions comprising: means for providing a roll attitude signal;   means for providing a roll command signal;   means for providing a modifying signal which is not derived from said roll attitude signal and which includes a multiplier having first and second signal inputs and a multiplied output representing said modifying signal;   means for combining said roll attitude signal and said roll command signal to produce a roll steering signal; and   means responsive to said modifying signal for modifying said roll attitude signal during non-zero roll attitude flight conditions and zero roll command to produce a zero roll steering signal.   
     
     
       11. The system of claim 10 wherein said first and second signal inputs are yaw rate and true air speed.